Is your feature request related to a problem? Please describe.
Currently, it's not clear where, and on what, the flags coming from MixEnvironment operate on.
E.g.

--keep makes sure a single environment variable transfers over.
--unset makes sure a single environment variable is removed from the environment.
--unset-environment clears the entire environment before doing anything else.

Out of these 3, only 1 makes it clear that it's operating on the environment.
The other 2 are quite generic in their naming, i.m.o.

Describe the solution you'd like

Have more verbose/better names for these flags.
E.g.

--set-env-var vs --set-var, or --add, or --set
--unset-env-var vs --unset
--keep-host-env-var vs --keep
--ignore-host-env vs --ignore-environment

Describe alternatives you've considered

• Not doing anything
• Only allowing people to set environment variables à la Docker CLI
• Adding the set flag to extend the environment

Additional context

Ref: #11490 (comment)

Priorities

Add 👍 to issues you find important.